This invention relates to a blank construction for making corrected custom orthopedic devices, or orthoses, for the foot can be fabricated. Such devices are commonly referred to as "foot orthotics".
The human foot is formed of a complex array of twenty-six bones. The human foot performs two main functions, support and locomotion. Ideally, the foot functions as a tripod, supporting the body's weight on the heel and across the metatarsal arch. The foot is capable of a wide range of movement. Under stressed conditions, one of the most important of these movements is the side to side rotation of the foot, either to the outside ("supination") or to the inside ("pronation"). This rotation increases or decreases the height of the foot's arch, and if excessive, can put the foot in a weakened, unbalanced, condition. The foot is said to be in a "neutral" position when it is neither pronated nor supinated, i.e., then the heel bone is vertical and is directly in line with the talus bone above it. The neutral position provides good skeletal support for the body's weight.
It is well known that activities which involve movement of the body, including walking, running, skiing, and skating, place very large stresses on the bones and joints of the leg and the foot. These stresses are larger when the bones and joints of the foot are not in the proper position, and are maximized when the knee is additionally out of proper alignment.
Improper foot structure and position have been treated in part through custom-molded foot orthotics which fit into the shoes and which support the foot, or parts of the foot, in a "corrected" position. This corrective function of a foot orthotic distinguished it from a mass-produced foot pad or other shoe insert designed strictly for comfort.
Orthotics are made from a custom impression or image of the foot. Impressions are typically made by plaster casting or by a mold of low density foam. Images of the feet also can be made by scanning or digitizing the foot and capturing that data in a computer database. Impressions are usually made with the subtalar joint in the neutral position. Depending on the process used, impressions can be taken in a weight bearing, semi-weight bearing or non-weight bearing position. At this point, generally through a practitioner's diagnosis, adjustments will be made to the impression or image to correct for biomechanical deficiencies. These adjustments are referred to as `postings`.
Postings can be placed into two general categories. Postings which involve modifications to the foot form are generally considered intrinsic postings as making an excavation in the foot form to accommodate a dropped metatarsal head. The result is a positive metatarsal lift in the orthotic molded over this form. The opposite type of posting is referred to as extrinsic. An example of this modification is to place a pad on the foot form directly over the dropped metatarsal head. An orthotic molded over this form has a relief pocket under the metatarsal head.
Other modifications can be added to an orthotic. These include but are not limited to rearfoot and forefoot wedges, heel lifts and metatarsal raise pads.
Orthotics can be fabricated either manually or by an automated process. Typically, a laboratory is used to fabricate the appliance. Most labs have cast scanning capability that work either with their own milling machine or a downstream miller. Due to the high cost of CAD-CAM milling, labs may not be able to afford their own miller. Central or shared fabrication facilities are common. Relay stations exist which scan and modem data to a central fabrication facility. Quite often casts are being measured, interpreted and then milled in three different sites and quite possibly by three different organizations. Usually, three or four visits to the medical practitioner are required while the shape of the patient's foot adjusts to the orthotic in use to progress to a final foot shape most comfortable to the patient.
A wide spectrum of materials are available to the practitioner to fabricate an orthotic. All orthotic materials have a certain degree of flexibility and a certain degree of rigidity. Materials as common as leather and cork can be used to fabricate orthotics. Other materials such as ethylene vinyl acetate (EVA), polyethylene and polypropylene are employed. These materials can be used alone or in combination with each other. Also important to the function of the orthotic is thickness and form.
There are several problems associated with the existing methods for fabricating foot orthotics. The single largest disadvantage is the impression processes employed. They do little to change the positioning and/or alignment of components of the foot. The molding and scanning processes used simply duplicate the structure of the foot. All modifications are done through the evaluation of the practitioner. Education and experience aid a practitioner in making proficient adjustments. However, these adjustments are still based on judgement.
Another disadvantage to the present processes is the time delay associated with fabricating the orthotic. Once the impression of a person's feet have been taken, a wait of several days or even several weeks is usually required before the orthotic is finished. When a patient has come to a practitioner with a foot problem, they usually require a remedy as soon as possible.
The break-in period associated with most presently available orthotics is also a disadvantage. Since modifications and adjustments to the impression are based on the inexact ability and judgement of the practitioner, the fabricated orthotic is often too uncomfortable for a person to wear for long periods of time when they first begin to wear it. Often, patients are told to wear the orthotics for short periods of time every day, increasing the amount of time over a period of weeks.
A foot orthotic must be suffiently flexible to provide comfort to the patient when positioned in the patient's shoe and must be sufficiently stiff to provide support under the weight of the patient during normal use of the patient. Foot orthotic blanks are disclosed in U.S. Pat. Nos. 4,813,090; 4,503,576 and 4,803,747. A method and apparatus for forming a foot orthotic is described in U.S. Pat. No. 1,044,171.
Accordingly, it would be desirable to provide a blank for a foot orthotic which conforms with the entire weight supporting surface of the foot. Furthermore, it would be desirable to provide such a foot orthotic which can be easily adjusted to a variety of foot sizes. Also, it would be desirable to provide such a foot orthotic which is sufficiently flexible to provide comfort to a patient and which is sufficiently stiff to promote support to the patient to provide therapy for the patient.